Field of the Invention
The present disclosure relates to a device and a method for controlling the temperature of a multi-resonant optoelectronic device, in particular comprising a ring-shaped optical microresonator.
Description of the Related Art
FIG. 1 shows an example of a ring-shaped microresonator 10 comprising first and second waveguides 12, 14 having a ring-shaped waveguide 16 arranged there between. An input light signal SInput is supplied at one end, called Input, of first waveguide 12. Optical coupling phenomena 12, 14, 16 may occur so that part of or an entire light signal SInput may be deviated by ring 16 towards second waveguide 14. Light signal SInput is then divided into a light signal SThrough emitted at the other end, called Through, of first waveguide 12, and a light signal SDrop emitted at one end, called Drop, of second waveguide 14. A possible light signal SAdd received at the other end, called Add, of second waveguide 14, may also be deviated towards ends Through and Drop of the ring microresonator.
FIG. 2 shows an example of a transfer function of microresonator 10 for end Drop and corresponds to the ratio of power PDrop of light signal SDrop to power PInput of light signal SInput according to wavelength λ of optical signal SInput. The transfer function exhibits a plurality of resonance peaks 18, two resonant peaks being shown in FIG. 2. Interval FSR between two adjacent resonance peaks is called free spectral interval. The free spectral interval may be expressed in frequency or in wavelength. Resonance peaks 18 are obtained for each wavelength of input signal SInput for which the optical path of the light signal in ring 16 corresponds to the product of the refraction index of the guide and of an integer multiple k of the wavelength. Integer k is called order of the resonance.
According to the provided use of microresonator 10, the transfer function may in particular be modified by the application of a voltage across an electric junction at the level of ring-shaped waveguide 16.
An optoelectronic device may comprise a plurality of series-connected ring-shaped microresonators, the resonance peaks being offset from one microresonator to the other. Such a device enables, in particular, to implement a method of data transfer with a wave division multiplexing (WDM) where a plurality of signals at different wavelengths may be simultaneously transmitted.
Waveguides 12, 14, 16 of microresonator 10 may correspond to silicon tracks surrounded with silicon oxide. A disadvantage is that the refraction indexes of the materials forming waveguides 12, 14, 16 vary according to temperature. This causes a shift of the transfer function of microresonator 10 when the temperature of ring 16 varies.
FIG. 3 is a drawing similar to FIG. 2 and illustrates the shift of the transfer function of microresonator 10 towards large wavelengths when the temperature of ring 16 increases. This shift is called redshift. In particular, power PDrop obtained for wavelength λ′ is greater in FIG. 3 than in FIG. 2. Conversely, when the temperature of ring 16 decreases, the transfer function shifts towards short wavelengths. This shift is called blueshift.
There exist devices capable of maintaining the ring 16 of a microresonator 10 at a constant temperature to stabilize the transfer function of microresonator 10. A possibility is to provide a heating element close to ring-shaped waveguide 16 controlled by a control device so that the temperature of ring 16 remains substantially constant, for example to within 0.1-0.2° C.
However, in certain cases, particularly when the ambient temperature varies too much, it may not be possible to maintain the ring temperature at a substantially constant value, for example, to within 0.1-0.2° C. Further, the control of the heating element may cause a significant electric power consumption. Further, the heating element does not enable to cool down the ring if the ambient temperature exceeds the target temperature.
Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplification set out herein illustrates an embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.